1. Field of the Invention
The present invention relates to a film unit assembly for employment in a diffusion-transfer process, and more particularly to a film unit assembly permitting simplified construction of film units, and simple removal of film units from a camera.
2. Description of the Prior Art
There is known conventionally a photographic process termed diffusion-transfer process, wherein development, as well as exposure, of a film is effected in a camera, thus making it possible to obtain a positive print of an object almost immediately after a film is exposed. The film employed in this process is constituted by a series of independent, sheet-like units, each of which corresponds to one frame for production of one photograph, and comprises a photosensitive layer, on which a negative image of an object may be formed upon exposure of the layer to light reflected from the object, and a positive image layer, which is in close proximity, or immediate juxtaposition to the photosensitive layer, and is bonded thereto at least along the edges, and onto which an image corresponding to a negative image formed on the photosensitive layer may be transferred under the influence of a suitable processing solution, which is spread between the layers. The processing solution is normally held in a container, which is attached to the photosensitive layer and positive image layer assembly, and is broken open under the action of rolls, or similar pressure means provided in an associated camera, these rolls also causing the processing solution to be spread throughout the film unit, and effecting, or assisting, removal of the film unit from the camera. As well as promoting development of photographic images, the processing solution is generally made viscous, and thus assists bonding of different layers of a film unit. In addition to photosensitive and positive image layers, each film unit usually comprises a transparent support layer, and a light-reflecting layer against which a developed photograph may be viewed. Also, since film units are packed in immediate juxtaposition to one another in a film pack, in order to ensure that, when a foremost film unit is exposed, light does not pass completely through this film unit and partially expose or fog other film units, it is essential to provide means for lightproof protection of successive film units lying to the rear of the exposed film unit. This lifhtproof protection may be provided in the form of an opaque layer incorporated in each film unit, or may be provided as separate lightproof sheets associated with the film units. In one case, construction of a film unit itself is rendered more complex, and in the other case, film unit assembly is made more difficult and in using the film pack, complicated, and a camera having a relatively complex construction is required.
It is accordingly an object of the present invention to provide a film unit assembly permitting simplified film unit construction, and ensuring lightproof protection of film units which it is not intended to expose.
It is another object of the invention to provide a film unit assembly which ensures lightproof protection for film units, but permits simple removal of film units from a pack and camera.
It is further object of the invention to provide a film unit assembly permitting temporary unloading of film units from a camera without risk of exposure thereof.